The present invention relates generally to molding machines, wherein mold parts and their platens are pressed and retained together during a molding process. Tie rods extend between and secure the mold part platens together during the molding process, and are separated to release the molding product. The present invention is especially applicable to large, high tonnage injection molding machines.
Injection molding devices or apparatuses typically include separable mold parts which are movable between open and closed positions. When the mold parts are closed together, a mold cavity is defined therebetween for receiving injected material, which is introduced therein in a fluid state under high pressure. After the injected material has hardened, the mold parts are opened or separated and the formed product is removed from one of the mold parts.
After a product is molded between the mold parts of a conventional molding machine, there is a down time or delay while the molded product is removed from the molding machine. The molding machine cannot mold a second product until the first molded product has been completely removed from the mold parts and the system is reset or realigned to mold the second product.
Also, because many molding machines remain aligned when the parts are separated, the operator may have to reach between the mold parts to remove the molded product and to prepare the mold parts for the next product. Therefore, it may be dangerous to remove the molded products from the mold parts of conventional molding machines, since an operator must reach or stand between the mold parts to access the molded product. U.S. Pat. No. 4,708,625 discloses a reaction injection molding (RIM) machine which books the platens and mold parts to provide safe access to the mold parts between molding processes.
Because the fluid material is injected into the mold part cavity under high pressure, the mold parts tend to separate during the molding process. As the size of the systems increase, the forces tending to separate the mold parts are correspondingly increased. Typically, the injection molding apparatus includes a platen at each of the mold parts. The tie rods extend between the platens and secure the platens relative to one another such that the mold parts are joined together, in order to resist the forces tending to separate the mold parts and platens during the molding process.
The tie rods extend a predetermined length from one of the mold parts and typically require a mold height adjustment in order to accommodate mold parts of different depths or heights. The tie rods are adjusted to extend an appropriate amount from one of the platens, such that when the two platens are moved to their engaged position, the tie rods extend a sufficient length for engaging and securing to the other platen. Typically, the mold height adjustment is accomplished via a mechanical adjustment of the tie rod. The tie rods are then extended the appropriate amount from the platen in which they are mounted.
Typically, the tie rods are positioned at various locations around the platens and may surround the mold parts. Because the tie rods typically are not movable with respect to one of the platens, the tie rods may interfere with access to the mold parts and the mold part cavity. This concern is even greater with larger injection molding apparatuses where a greater number of tie rods may be required to resist the forces tending to separate the mold parts. The position of the tie rods thus may result in limiting the size of a part which can be molded by a particular molding apparatus, and may further result in the removal of the molded part becoming a difficult and even dangerous process.
One proposed system is disclosed in U.S. Pat. No. 5,417,913, which provides tie rods which are movable relative to the platens, such that the tie rods may be spaced from the gap between the platens when the platens are separated. This allows for easier access to the mold parts when the platens and mold parts are separated.
When multiple colored or multiple layered items or products are molded by an injection molding machine, a single color or portion of the product or item is molded at one time. In such applications, multiple mold parts are typically spaced on one of the platens, whereby a color or portion of the product is shot or molded separately at each of the mold parts. The mold parts are then indexed so the next mold device can mold the second color or portion of the product. Because multiple mold parts for the different portions of the product are spaced on the platens of the molding apparatus, the size of the product must be small enough to utilize only a portion of the platen, in order to provide room for the other mold parts for other portions of the product about the platen. Furthermore, because the size of the mold part that is available for molding a product is determined by the size of the platens and by the position of the tie rods about the mold parts, a larger machine may be needed to mold multi-colored products or a given machine may be limited to molding smaller products. Accordingly, the process for molding multiple colors or layers of products may require removal of the partial product to place the partially molded product in a second mold cavity for subsequent molding of a second or third portion of the product.
Therefore, there is a need in the art for a molding apparatus which provides movable tie rods which are easily adjustable and movable to also provide clearance and access to the mold part platens when the platens are separated. The tie rods should also be adjustable to account for mold height variation for different mold parts. Also, there is a need for a molding apparatus which provides safe and easy access to the mold parts between molding processes. There is a further need in the art for a molding apparatus which is capable of molding multicolored parts in an efficient and effective manner.
The present invention is intended to provide a molding apparatus which provides movable tie rods which are retractable such that the tie rods are removed from the gap between the mold platens when the mold platens are separated, thereby easing access to the mold parts. The present invention is also intended to provide a molding machine which enhances access to the molded product via booking of a fixed platen for access to the molded product. The present invention may also provide simultaneous molding of a second product while the first product is booked for removal, thereby increasing the efficiency of the system.
According to an aspect of the present invention, a mold assembly for molding products between a pair of mold parts comprises a support base, a fixed platen support positioned at a first end of the support base, and at least one movable mold module which is movably supported along the support base toward and away from the fixed platen support. The fixed platen support includes at least one fixed platen which supports one of the pair of mold parts. The movable mold module includes a movable platen carriage, which supports a movable platen, which further supports the other of the pair of mold parts. The movable platen carriage is movable along the support base toward and away from the fixed platen support. The movable platen is movable between an engaged position, where the mold parts are engaged together for molding, and a separated position, where the mold parts and platens are separated. The movable mold module further includes at least one tie rod assembly movably mounted at the movable platen carriage. The tie rod assembly is movable with respect to the movable and fixed platens. The tie rod assembly is initially removed from proximity of the mold parts when the mold parts and platens are separated and is movable along the movable platen carriage to extend from the movable platen carriage and engage the fixed platen support to maintain engagement of the platens and the mold parts during the molding process.
Preferably, the tie rod assemblies are mounted to a tie rod carriage which is movable along the movable platen carriage to move the tie rod assemblies relative to the movable platen carriage and the platens. Preferably, each of the tie rod assemblies comprises a tie rod, which extends from a piston within an hydraulic cylinder, which is mounted to the tie rod carriage. The piston and tie rod are movable relative to the cylinder via pressurized hydraulic fluid to adjust a length of the tie rod extending from the cylinder for a mold height adjustment. The tie rods extend from the tie rod carriage and the movable platen and are insertable at least partially through the fixed platen. Preferably, the pistons and tie rods are rotatable relative to the cylinder and tie rod carriage to lock the tie rods to the fixed platen after they have been engaged therewith.
In one form, the movable platen carriage is movable along the support base with an injector carriage which supports an injection machine thereon. Alternately, a reaction injection molding machine may be positioned at or remote from the movable platen carriage.
In one form, the fixed platen support includes at least two fixed platens and is pivotable to align one of the fixed platens with the movable platen, while allowing access to the other of the fixed platens. The assembly may further comprise two or more movable mold modules, whereby the fixed platen support is pivotable to align the fixed platens with a corresponding one of the movable mold modules. By the term xe2x80x9cfixedxe2x80x9d platen, it is meant that the platen is xe2x80x9cfixedxe2x80x9d during the molding processes and is not movable toward and away from the other, movable platen of the molding apparatus, although the xe2x80x9cfixedxe2x80x9d platen may be pivotable or movable between molding processes to cycle the fixed platens between multiple mold stations and/or access stations. Preferably, the fixed platen support is pivotable to pivot a partially molded product and corresponding mold part and first fixed platen from one of the movable mold modules to a next one of the movable mold modules, whereby a different color or portion of the product is molded between the respective mold part of the next movable mold modules and the mold part of the first fixed platen.
According to another aspect of the present invention, a molding assembly for molding items with an injection machine comprises a support base, at least one movable platen which is movable along at least a portion of the support base, and a fixed platen support structure which supports at least two fixed platens. The fixed platen support structure is pivotally mounted to the support base and is pivotable about a generally vertical axis to align at least one of the fixed platens with at least one of the movable platens, while another of the fixed platens is either aligned with another movable platen or booked for access thereto. In one form, the molding assembly includes at least two movable platens, each of which is movable along a different portion of the support base toward and away from the fixed platen support. Optionally, the fixed platen support is pivotable to move one of the fixed platens from one of the movable platens to another of the movable platens, whereby a different layer or portion of an item being molded by the molding assembly is molded at each of the movable platens. Preferably, the molding assembly includes at least one tie rod which is engagable between the movable platen and at least one of the fixed platens to secure the platens relative to one another during the molding process.
According to yet another aspect of the present invention, a method for molding multiple portions of a product or item in a molding machine comprises providing a molding machine, which includes a base, a fixed platen support movably or pivotally mounted at the base, and first and second movable platens movably mounted at a respective portion of the base and movable therealong toward and away from the fixed platen support. The fixed platen support includes first and second fixed platens mounted thereon and is movable to move the first and second fixed platens between aligned positions with the first and second movable platens. A first product or portion of a product is molded between the first movable platen and the first fixed platen. The fixed platen support is then moved or pivoted to move the first fixed platen and the first product from alignment with the first movable platen. A second product or portion of a product is molded between the second movable platen and the first or second fixed platen.
In one form, the molding machine may be operable to mold different products generally simultaneously between the respective movable and fixed platens. The fixed platen support is movable or rotatable to move the molded product to an access station after the product is molded.
In another form, the molding machine molds first and second portions of a product, such that the first portion is molded between the first fixed platen and the first movable platen, and the second portion is molded between the first fixed platen and second movable platen. After both portions are molded, the fixed platen support is then pivoted to move the first fixed platen and the molded item away from the first and second movable platens for removal of the molded item. Preferably, a first portion of another item is molded between the first movable platen and the second fixed platen while the second portion of the first item is being molded between the second movable platen and the first fixed platen.
According to another aspect of the present invention, a mold assembly for molding products with a molding machine comprises a first platen and a second platen and at least one tie rod assembly. The tie rod assembly includes an hydraulic cylinder movably mounted at the first platen. The first and second platens are oppositely facing one another and support a respective mold part thereon. The platens are movable relative to each other between an engaged position for molding an item between the mold parts and a retracted position, whereby a gap is between the platens and the mold parts. The tie rod assembly includes a piston which is movable within and along the cylinder and includes a tie rod extending from one end of the piston. The tie rod assembly is initially retracted and remote from the gap between the platens when the platens are in the retracted position. The cylinder is movable relative to the first platen to move the tie rod to an extended position, whereby the tie rod is moved toward the second platen and may lock the first and second platens in the engaged position. The piston and tie rod are rotatable relative to the cylinder to lock the tie rod at the second platen. The piston of the tie rod assembly is also longitudinally adjustable relative to the cylinder to adjust an amount of extension of the tie rod from the cylinder to account for a thickness or depth of mold parts and/or a separation of the first and second platens when in the engaged position. Preferably, the second platen is generally fixedly mounted to a base and the first platen is mounted to a movable support which is movable along the base. The movable support is movable to move the first platen between the separated position and the engaged position with respect to the second platen. Preferably, the tie rod assembly is movably positioned at the movable support.
Therefore, the present invention provides a molding apparatus which includes an injector and tie rods on a single movable mold module which engages a fixed platen at a fixed platen support. The fixed platen support may be movable or pivotable to align fixed platens with one or more movable mold modules, whereby multiple layers or portions of items or multiple items may be simultaneously molded at different stations of the mold assembly, thereby substantially improving the efficiency of the molding apparatus. Preferably, multiple items or portions of items may be molded simultaneously at different stations positioned around a single fixed platen support which includes multiple platens thereon. The fixed platen support may be movable or pivotable to move the portions of the parts from the movable mold module and injector to the next mold module or to move each completed item from a movable mold module to an insert or access station for easy access to the molded product. The tie rods are movable with respect to the movable platens and thus may be removed from proximity to the mold parts when the mold parts and platens are separated, thereby improving access to the mold parts between the molding processes.